snakes are sold in pairs because only worms are sold in apples..... badumbum.
Like others have said, although you don't see it as much anymore, snakes have often been sold in 1.1 pairs because otherwise the breeder will end up with a bunch of males which are harder to sell (to other breeders, which is usually their biggest client base). However if your goal is not breeding you could requeste a single male for a pet and most breeders would be happy to accomodate you.
However if your goal IS breeding, and you're worried about inbreeding, you can always buy another pair from another breeder and swap the males. However, I've never found inbreeding to be that much of a problem with snakes.